SAN FRANCISCO (CBS 5) — California’s strict gun control laws are under fire as a result of a CBS 5 investigation into a device called the “bullet button,” which makes an AR-15 or AK-47-type gun legal in the state. The debate over the device has the state’s top cop dodging our questions and one lawmaker receiving threats.

From billboards to merchandise, the attack on State Senator Leland Yee’s gun control bill SB 249 is organized, and getting vicious. His office is getting threatening calls, with some telling him to go back to communist China and other racially charged statements.

“Unfortunately there are many individuals in the state and in this country that look to the bill that I am carrying as really un-American. And I will tell you that I am probably as American as anyone else,” Yee said.

The senator introduced the bill after seeing a CBS 5 report that showed people at the range firing semi-automatic rifles, even though California has a strict assault weapons ban.

“The reason why I am committed to this particular bill is because of what I saw on your TV station, the story that you did,” Yee told CBS 5.

We discovered it all came down to a tiny device called a bullet button. It allows one to quickly detach a magazine, even though under California law detachable magazines in combination with other features are illegal.

But under California regulations, the bullet button makes a gun’s magazine “fixed” and therefore legal, because one needs a tool, such as the tip of a bullet, to detach it.

Yee’s bill originally sought to ban the bullet button. But he recently amended the bill to ban only conversion kits such as the “mag magnet,” a hot seller at gun shows, that makes a bullet button even easier to use.

The senator answered: “Given all the opposition we have had thus far, I think that this probably would be a way that we can craft a bill that would pass muster.”

But gun rights advocates are still against Yee’s measure. “This is a misguided gun control bill that is only going to further complicate California’s already draconian gun control laws,” said Yih Chau Chang. He runs Responsible Citizens of California, a group that advocates for the right to carry firearms.

Even if it passes, Chang said, “It will do nothing to stop either the mag magnet or the bullet button.”

In this case, even leading gun control organizations agree. “Even if Senator Yee’s legislation is passed, there would still be a whole bunch of guns that it doesn’t apply to,” said Dan Gross, President of the Brady Campaign to Prevent Gun Violence.

If approved, firearms with factory-installed bullet buttons would still be legal. All the major manufacturers are making them and gun stores all over the Bay Area are selling them.

“While we certainly appreciate the spirit of Senator Yee’s legislation, this isn’t an issue that is best dealt with that way,” said Gross.

In an urgent letter to California Attorney General Kamala Harris, the Brady Campaign is calling on her to plug the loophole, by fixing the state’s “unlawful assault weapons regulations.”

Gross said, “There’s an opportunity now under current law to make it very clear that these guns should not be bought or sold. This is a very important issue, people have the potential to die as a result and you know if I were Attorney General I wouldn’t want that on my conscience. She needs to take action,” said Gross.

But the Brady Campaign and CBS 5 has not heard back from the Attorney General. After months of trying to get an answer, CBS 5 caught up with Kamala Harris at a press conference in San Francisco, asking her what she was going to do about the state’s regulations.

“We’re taking a look at the issue and I’m happy to follow up with you and let’s make sure that we do,” she said.

Harris agreed to meet with CBS 5 in the hall, asking her press secretary Lynda Gledhill to “set it up.” But Gledhill didn’t seem happy about our request at all. “Ok, I am sorry. I have a roomful of reporters I have to deal with right this second can you wait right here for a second? Is that possible?” she said.

As CBS 5 waited, everyone left. Another press official said, “The Attorney General is not there any more. I think she and her staff may have gone out the back.”

The Attorney General’s staff later promised CBS 5’s Allen Martin that Harris would sit down for an interview on the issue, possibly by the end of the month.

The Brady Campaign is threatening a lawsuit if the Attorney General doesn’t change the state’s regulations on assault weapons. Meanwhile, the gun rights group Calguns has already sued the California Department of Justice in federal court, claiming the law is unconstitutionally vague.

(Copyright 2012 by CBS San Francisco. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)